DESCRIPTION (Verbatim from Applicant's Abstract): This resubmission continues the overall goal which is to develop and apply an x-ray micro-CT scanner for generating 3-D images, of sufficient spatial resolution and specimen size, to allow quantitation of intact organ microarchitecture in terms of all Basic Functional Units (BFU, e.g., glomerulus and its nephron) as well as the transport mechanisms within the organ. The application is focused on intact rodent organs or similar-sized (1-8 cm3) "biopsies" from large animals and humans. In response to the previous review, more detail of scanner characteristics and how these relate to users of the scanner, are provided. The hypothesis of this proposal is that bench-top x-ray micro-CT can provide important new quantitative information about organ micro architecture by a combination of hardware and software enhancements motivated by their utility in meeting new biomedical research needs, such as defining the phenotype of genetically modified mice. AIM I - expand the hardware and associated software to: (a) extend the capability of our current x-ray detection device with "super"-resolution scanning modes & reconstruction algorithms and with "local" reconstruction algorithms, (b) add helical scanning capability, (c) increase x-ray flux with x-ray optics. AIM II - Image dvnamic processes bv scanning 'snap' frozen specimen: This involves snap-freezing the specimen immediately after (a) the desired distribution of contrast agent or (b) degree of mechanical distortion (e.g., inflation) has been achieved in vivo and keeping it frozen during the scan. AIM III - Quantitation of 3-D microarchitecture and associated 3-D function by image analysis via (a) extension of automated vascular "tree" finding/analysis algorithm; (b) develop a visualization tool for guiding and evaluating the automated image analysis; (c) quantitation of local strains throughout an organ that is mechanically distorted during a scan; and (d) analysis of the fluid dynamic implications of vessel branching geometry. AIM IV - Continue to provide the 3D micro-CT imaging service to investigator-users so that this experience will guide innovation, improvement and/or expansion of the imaging repertoire of the micro-CT methodology.